The present invention relates to a process cartridge and an electrophotographic image forming apparatus for forming an image on the recording material, to which the process cartridge is detachably mountable.
Here, the electrophotographic image forming apparatus is an apparatus which forms an image on a recording material through an electrophotographic process. The electrophotographic image forming apparatus may be an electrophotographic copying machine, an electrophotographic printer (a LED printer, a laser beam printer or the like), an electrophotographic printer type facsimile machine, an electrophotographic printer type word processor or the like.
The process cartridge is a cartridge containing as a unit an electrophotographic photosensitive drum and a charge member, a developing member or a cleaning member, the unit being detachably mountable to the main assembly of the image forming apparatus. The process cartridge is a cartridge containing as a unit an electrophotographic photosensitive drum and at least one of a charge member, a developing member and a cleaning member, the unit being detachably mountable to the main assembly of the image forming apparatus. The process cartridge may contain as a unit an electrophotographic photosensitive drum and at least a developing member, the unit being detachably mountable to a main assembly of the electrophotographic image forming apparatus.
In an electrophotographic image forming apparatus using the electrophotographic image forming process, use has been made of the process cartridge type in which the process cartridge comprises as a unit the electrophotographic photosensitive member and process means actable on the electrophotographic photosensitive member, the unit being detachably mountable to the main assembly of the electrophotographic image forming apparatus. With the use of the process cartridge type, the maintenance operation can be carried out in effect by the users without the necessity of relying on serviceman, and therefore, the operativity is improved. Therefore, the process cartridge type is widely used in the field of electrophotographic image forming apparatus.
Such a process cartridge has the following structure to maintain a proper positional relation between the photosensitive drum and the developing roller to provide stabilized image quality.
The cleaning unit having the photosensitive drum and the developing unit having the developing device are coupled rotatably by a pin, and the photosensitive drum and the developing roller are pressed to each other by a pressing spring. Here, the developing roller is provided with rotatable rollers. By this, there is distance between the axes of the photosensitive drum and the developing roller. Here, the diameter of the rollers is larger than the diameter of the developing roller, and by the press-contact between the photosensitive drum and rollers by the spring force of the pressing spring, the gap is maintained between the photosensitive drum and the developing roller.
FIG. 19 illustrates an example of a driving training for the process cartridge 103. The driving force is transmitted to the process cartridge 103 by the driving gear 153 and the drum gear 4. The driving gear 5 is in meshing engagement with the drum gear 4, and the driving force is transmitted through the drum gear 4. The driving gear 5 drives the developing roller and also transmits the driving force to the toner stirring gear 8 through idler gears 6, 7.
A description will be provided as to the positioning of the process cartridge 103 relative to the main assembly of the apparatus. As shown in FIG. 20, a longitudinal end of a process cartridge 103 is provided with an engaging portion 40 for engagement with a guide portion 160 provided in the main assembly of the apparatus. By doing so, when the process cartridge 103 is inserted into the main assembly of apparatus, the engaging portion 40 is inserted along the guide portion 160, and the correct positioning is accomplished by abutment to the stopper 161 provided in the main assembly of the apparatus. At this time, the drum gear 4 of a process cartridge 103 is brought into engagement with a driving gear 153 provided in the main assembly of the apparatus.
When the driving force is applied to the process cartridge 103, an engagement force F1 is produced in a direction deviated by an engaging pressure angle from a normal line L1 on a line connecting the centers of rotation of the drum driving gear 4 and the driving gear 153 at a pitch point. By this, the process cartridge 103 is pressed against the stopper 161 of the main assembly of the apparatus. Thus, the force is produced substantially perpendicularly to the axial direction of the photosensitive drum 1, and the positional deviation of the cartridge 103 can be suppressed.
However, with this structure, as shown in FIG. 19, when the cartridge 103 is driven, the driving force for the developing unit 152 is concentrated in the direction E of engagement between the drum gear 4 and the driving gear 5. Therefore, as seen in the longitudinal direction of the process cartridge 103, a twisting force is produced. In order to avoid deformation of the frame due to such a force so as to stabilize the image quality, it is conventional that the frame of a process cartridge 103 is reinforced, or the spring forces of the left and right pressing springs are made different from each other. By doing so, a balance is provided against the twisting of the frame. The above-described structure is very good and effective to avoid the deformation of the frame, thus stabilizing the image quality.
The present invention provides a further development of the above described structure.
Accordingly, it is a principal object of the present invention to provide a downsized and light weight process cartridge and an electrophotographic image forming apparatus to which the process cartridge is detachably mountable.
It is another object of the present invention to provide a process cartridge in which the deformation of the frame thereof is effectively prevented despite the fact that thickness of the frame is reduced in order to reduce the size and weight of the process cartridge, and to provide an electrophotographic image forming apparatus to which the process cartridge is detachably mountable.
It is a further object of the present invention to provide a process cartridge in which when the driving force is applied from the main assembly of apparatus to the process cartridge, the moment about the center of the frame provided by the engaging force of the gears can be suppressed, to provide and an image forming apparatus to which the process cartridge is detachably mountable.
According to an aspect of the present invention, that is provided a process cartridge detachably mountable to the main assembly of an electrophotographic image forming apparatus, the process cartridge comprising a first frame; a second frame connected with the first frame for rotation about a shaft; an electrophotographic photosensitive drum provided in the first frame; a developing member, provided in the second frame, for developing an electrostatic latent image formed on the photosensitive drum with a developer; and a development driving force receiving member for receiving a driving force for rotating the developing member from a main assembly of the apparatus when the process cartridge is mounted to the main assembly of the apparatus, the development driving force receiving member being disposed coaxial with the shaft.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
According to another aspect of the present invention, there is provided an image forming apparatus to which the process cartridge is detachably mountable.